Field of the Invention
In previous types of double flapper-type check valves, hinge and stop pins are installed through holes which extend through the wall of the valve body. After installation of the pins, the holes are sealed by plugs or other means. While initially effective, there is a possibility of leakage from the inside to the outside past the seals.
Another disadvantage of current designs is that the flappers are free to move sideways in the bore due to the need to permit downstream movement of the flappers, necessary to avoid interference of the heels of the flappers with the seat when the flappers rotate to the open position. This movement causes extra wear on the wall of the flapper hinge or bushing, depending upon actual design.
One modification made to avoid holes through the wall is to mount the pins in inserts which fit into cavities machined into the inner surface of the body wall. These inserts are retained in place by various means U.S. Pat. No. 4,694,853 describes and illustrates the various embodiments in which hinge pins and stop pins are mounted in inserts positioned in recesses in the body wall.
Although holes through the body wall are eliminated, and thus also potential leak paths, the modifications using inserts are expensive to manufacture and the design can restrict the particular type of gasket that can be used. Also, thinning of the wall occurs, which is not desirable.
The present invention avoids the need for holes through the body wall and also avoids the need to machine recesses in the body wall. Sideways movement of the valve is also eliminated. It is possible to eliminate the need for a stop pin.
Broadly, in accordance with the present invention, a fluid valve comprises a valve body having a bore therethrough, having an annular seat in the bore. A flapper assembly is positioned in the bore, and comprises a pair of substantially semi-circular flapper members, a pair of spaced holding members having elongate bores extending axially in the holding members, the outer surfaces of the holding members of the same profile as the bore in the valve body. A hinge pin is mounted at each end in the elongate bores and pivotally mounts the flapper members. Retaining means extend into the bore of the valve body, the holding members positioned between the seat and the retaining means.
In accordance with one embodiment of the invention, the retaining means comprises two diametrically opposed projections, and locating means position the flap assembly in the bore with a hinge pin aligned with the projections.
In another embodiment, the retaining means comprises a resilient member, of annular form, seated in a groove in the bore.
A stop pin may also extend between the holding members, aligned with the hinge pin, on the side remote from the seat.
The invention will be readily understood by the following description of certain embodiments, by way of example, in conjunction with the accompanying drawings.